Exchange progressbar with progress (#211)

This PR addresses issue #211

I thought, I'd kick this off with a first implementation of using progress. The change was easy enough and it is easy to handle.

It still needs a test for a website with no content-header and I would need a site with a larger downloadable file without a content-header to see how the spinner works.

I know it still needs work, but I would appreciate some input, if we should go ahead with it.

Cheers 
Sadly, no. I checked in the code. When `max=None` it is automatically set to `100`

So it would have to be like that or a different library. Is that a deal breaker?

I'm still not sold on this library. It is easy to use, but if I had more time, I would write my own one with the specifications you mentioned ;)